1. Technical Field
This invention relates to fluid flow sensing devices that use fiber optics, and more particularly to those sensing devices that are disposed on the exterior of a conduit.
2. Background Information
In the petroleum industry, there is considerable value in the ability to monitor the flow of petroleum products in the production pipe of a well in real time. Historically, flow parameters such as the bulk velocity of a fluid have been sensed with devices directly disposed within the fluid flow. These type devices have several drawbacks including the fact that they provide an undesirable flow impediment, are subject to the hostile environment within the pipe, and typically provide undesirable potential leak paths into or out of the pipe. Sensors disposed outside the fluid flow pipe avoid these problems, but can be subject to other difficulties stemming from the well environment, which is often characterized by extreme temperatures and pressures. Extreme temperatures can disable and limit the life of electronic components. Sensors disposed outside of the production pipe may also be subject to environmental materials such as water (fresh or salt), steam, mud, sand, etc.
What is needed, therefore, is an apparatus that can protect flow sensing devices that are disposed outside a pipe, and one that can protect sensing devices in a well environment characterized by extreme temperatures and pressures and the presence of debris.
It is, therefore, an object of the present invention to provide an apparatus for protecting flow sensing devices that are disposed on the exterior of a pipe, and one that can protect sensing devices in a hostile environment.
According to the present invention an apparatus for non-intrusively sensing fluid flow within a pipe is provided. The apparatus includes an array of sensors that include a plurality of optical fiber coils. The array of sensors senses the fluid flow inside the pipe. At least one optical reflective device is disposed between adjacent optical fiber coils. An isolation pad is disposed between each optical reflective device and the pipe.
An advantage of the present invention is that it enables the collection of data pertaining to fluid flow within a pipe in a non-intrusive manner. An externally mounted sensor for non-intrusively sensing fluid flow within the pipe can be subjected to pipe growth and/or vibrations. In those instances where an optical reflective device is utilized with a sensor, the isolation pad isolates the optical reflective device, and splices if used, from thermally or mechanically related pipe growth and/or vibrations. Error or damage that might otherwise be caused by the pipe growth and/or vibrations is thereby decreased to an acceptable level. In some applications, the isolation pad may be used directly under a sensor to protect the sensor.
The present apparatus is also protected from the environment by a compactly formed housing that encloses the array of sensors and the isolation pad. In a well environment, the housing protects the array from fluid and debris that may enter the annulus between the production pipe and the well casing.
The foregoing and other objects, features, and advantages of the present invention will become more apparent in light of the following detailed description of exemplary embodiments thereof.